The purpose of these studies is to identify possible candidate industries, labor unions and workplaces with occupational exposures to welding fumes (WF) with special emphasis on manganese (MN) and recruit their participation in an exposure assessment study. NIOSH has identified a specific need for assessing the neuropsychiatric effects of WF, as concern was noted for the potential of manganese (Mn) in welding fume to cause neurotoxicity in exposed workers. This study will measure workplace exposures of welders, especially those exposed to appreciable levels of Mn, often associated with mild-steel and stainless steel welding operations. Manganese in WF complexes with many other metal elements, chiefly iron, oxides, and fluoride and may exist in several valence states. The field survey phase of this study for the collection of area and workers breathing zone exposure samples concluded in FY12. A total of nine walk through site visits were conducted. Following these initial site visits, eleven comprehensive industrial hygiene sampling surveys were conducted at: a scientific appliance manufacturer; construction contractors at an oil refinery; a shipyard; heavy equipment manufacturing factories; an oil refinery turn-around (i.e., inspection, demolition and rebuilding process equipment); a specialty parts welding shop; and a custom structural steel fabricator building large supports for bridges, caissons, tug boats, flood gates, and tunnel boring equipment. Over three hundred full-shift worker-days of exposure have been sampled using both total and respirable particle size methods. These samples have either been or will be analyzed to measure four Mn fractions using a sequential extraction procedure and inductively-coupled plasma atomic emission spectroscopy (ICP-AES) analysis via NIOSH Manual of Analytical Methods (NMAM) draft 7305. Several dozen area sample sets have also been collected which will be analyzed by sequential extraction for Mn fractions; standard metal scan via NMAM 7303; x-ray defraction (XRD); and scanning and transmission electron microscopy (S/TEM) using X-ray mapping and energy dispersive X-ray analyses. The welders personal exposure samples have been chemically analyzed and the full-shift time-weighted average data were reported in the site reports for the first three facilities which have been submitted to the participating companies and unions. A SAS database was established in FY12 for future statistical analyses of this large data set. Quality check tests of the analysis methods have been completed at a contract laboratory and all workers breathing zone and area air samples have been submitted for Mn fractional analyses. A laboratory generated welding fume study was conducted in FY12 to more thoroughly validate the sequential extraction method for analyzing manganese fractions based on valence states and preferential solubility in different digestion solutions. The welding fume samples were generated within a chamber and bulk fume was collected by NIOSH collaborators in the Health Effects Laboratory Division, Morgantown, WV. These chamber samples were generated using several metal arc processes: gas metal arc welding (GMAW) ((i.e., MIG welding) operated in short circuit mode using mild carbon steel and stainless steel, and flux-core arc welding (FCAW) and shielded metal arc welding (SMAW) (i.e., stick welding) using mild carbon steel. Three of these bulk welding fume samples have been analyzed using the sequential extraction procedure for Mn fractions via draft NMAM 7305. Analysis of the fourth bulk fume sample is currently in progress.